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					High School Science                                                                    Electricity
Physics

                               SCoPE Site Lesson Plan
Title: Lesson 6—How Bright Is Your Light? (SC110306)

Abstract
Students set up series and parallel circuits with two high resistance bulbs and two low resistance
bulbs, and determine how they vary in brightness in various parts of the circuits.

Subject Area: Science

Grade Level and Course Title: Eleventh Grade/Physics

Unit of Study: Electricity

Benchmarks
    Ask questions about circuits that can be investigated empirically and justify explanations
     (I.1.HS.1, II.1.HS.1).
    Use combinations of bulbs with different resistances to show how current is affected in
     series and parallel circuits (IV.1.HS.4).

Key Concepts
circuit
current
potential difference
resistance

Instructional Resources
Equipment/Manipulative
Battery packs with 4 1.5 V cells (1 per group)
Copper wire (approximately 0.1 m per group)
Flash light bulbs - #48 round (3 per group)
Flash light bulbs - #14 long (1 per group)
Open bulb holders (4 per group)
Voltmeter (available to each group)

Student Resource
Cerrudo, Kim, and Juliana Texley. Unit 3 Lesson 6 Student Pages. Teacher-made material.
   Lansing, MI: Michigan Department of Treasury, 2004.

Cramer, Peter. PEARLS. CD-ROM. Raleigh, NC: Physics Academic Software, 1997.

Hewitt, Paul. Conceptual Physics. New York: Addison Wesley, 1997.

Hickey, et al. PhysWiz. CD-ROM. Raleigh, NC: Physics Academic Software, 1996.




March 17, 2004                                                     SCoPE SC110306 Page 1 of 4
High School Science                                                                      Electricity
Physics
Lambert and Bartlett. Lighting Up Circuits. CD-ROM. Raleigh, NC: Physics Academic
   Software, 1996.

Science Hobbyist Pages. Ed. Bill Beaty. 1994. 17 March 2004 <http://www.amasci.com>.

Teacher Resource
Beyond the Mechanical Universe. Laserdisc. Santa Barbara, CA: Intellimation, 1987.

Cerrudo, Kim, and Juliana Texley. Grade 11 Unit 3 Teacher Background. Teacher-made
   material. Lansing, MI: Michigan Department of Treasury, 2004.

C3P 2000+. University of             Dallas    Department      of   Physics.   17    March    2004
   <http://phys.udallas.edu>.

Huggins, E.R. Physics 2000: Introductory Physics. CD-ROM. Hannover, NH: Moose Mountain
   Digital Press, 2001.

Lessons in Electric Circuits. Ed. Tony R. Kuphaldt. 2000 – 2004. 17 March 2004
   <http://www.ibiblio.org/obp/electricCircuits>.

Sequence of Activities
Advanced Preparation: Divide complete sets of materials into small containers (plastic containers
from the grocery work well) for easy distribution.

Safety Precautions: Recharged batteries can vary in voltage.

1. Ask students to summarize the conclusions they have developed from their research in
   Lessons 2 through 5. For each conclusion, ask students to review the measuring tool and the
   units that they used in establishing their conclusions.
            Current is constant in all parts of a series circuit (ammeter, amperes).
            Resistance is an inverse function of wire diameter and a direct function of wire
                length (ohmmeter, ohms).
            Potential difference is the same in all parts of a parallel circuit (voltmeter, volts).
            In a parallel circuit current is inversely proportional to resistance (ammeter,
                amperes).
   Put these ideas on a bulletin board or a semi-permanent area of the chalkboard as a graphic
   organizer. Ask students to review the resistance of each of the types of bulbs they have used,
   long and round, from their Student Pages.

2. Pass out materials and guide students in reconstructing another series circuit as shown.
   Letters A and B are round bulbs; Letters C and D are long bulbs.




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High School Science                                                                       Electricity
Physics
                                              A




                                                                           B




                                                                           C




                                              D

3. Students should describe the brightness of each bulb based on their visual observations in the
   table below.

4. Students should place the leads of a voltmeter on either side of Bulb A and measure the
   potential difference. (If the reading is negative, they should reverse the leads.)

5. Repeat Step 4 for bulbs B, C, and D, recording all data.

6. Students should disconnect the series circuit and reconnect as a parallel circuit, as in the
   diagram below. A and B are round bulbs. C and D are long flashlight bulbs.




                                     A               B         C         D




7. Students should describe the brightness of each bulb in the parallel circuit in the table.

8. Ask students to repeat Step 4 for each of the bulbs and then record the data.




March 17, 2004                                                       SCoPE SC110306 Page 3 of 4
High School Science                                                                       Electricity
Physics


   Type of          Series Circuit                           Parallel Circuit
   Circuit
   Resistor         Long bulbs           Round bulbs         Long bulbs           Round bulbs
   Brightness
   Voltage

9. Discuss the results of the observations with the students. Remind students that the round
   bulbs were lower resistance than the longer bulbs. [In Step 3, the round bulbs will not light or
   light very dimly; the long bulbs will light. The current passing through the round bulbs is too
   low to light them. In Step 7 students should note that the round bulbs are much brighter than
   the long bulbs. In a series circuit, the high resistance bulbs limit the current passing through
   the circuit. The current is too low to light the low resistance bulbs. In the parallel circuit the
   brightness of the bulb decreases as the resistance increases because the potential difference is
   the same for each branch.]

10. Ask students to look again at their light bulbs. ―Could they describe how they are made?
    Could they make one? The first electric lights were produced by British chemist Humphry
    Davy in 1801. He created sparks between carbon rods connected to the poles of a battery.
    This is an arc light, and could be somewhat practical when generators were available to
    produce electricity. Davy also showed that light could be produced by heating a wire until it
    began to glow (an incandescent bulb) but unless there was a very good vacuum, the wire
    quickly burned up. The electric light was improved in 1865 when German Scientist Hermann
    Sprengel improved the vacuum pump.‖ Ask students why these developments are not as
    well known as Edison’s work. [These bulbs were expensive, impractical.] In the ―Extend
    Your Knowledge‖ section of the Student Pages students are asked to speculate on life before
    light bulbs. This will provide some preliminary thinking for Lesson 10.

Assessment
Students should be able to develop their own ―water hose analogy‖ to explain the differences
between the data they saw in the series and parallel circuits.

Application Beyond School
Students can research how the three separate light systems in cars are wired, and the differences
between high and low beam headlights.

Connections
Mathematics
When studying electrical circuits, students can use equation-solving techniques.




March 17, 2004                                                       SCoPE SC110306 Page 4 of 4

				
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